Changer mechanism for individual measurement of radioactive samples in a gamma counter

ABSTRACT

The invention relates to a changer mechanism for individual measurement of radioactive samples in a gamma counter. The changer mechanism comprises an identifying element for identifying sample containers of different sizes and a transferring device for transferring the sample containers to the measuring unit for measuring, and back therefrom after measuring. According to the invention, the changer mechanism comprises a lifting device having a grip unit for lifting and transferring the sample from the transfer unit to the measuring unit. The grip unit is provided with grip elements for transferring samples of different sizes based on the information obtained from the identifying unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a changer mechanism for the individualmeasurement of radioactive samples in a gamma counter, the changermechanism comprising an identifying element for identifying samplecontainers of different sizes and a device for transferring the sampleto the measuring unit for measuring and back therefrom after measuring.

2. Description of Related Art

Gamma counter measurements of radioactive samples are commonly conductedusing either RIA (Radio Immuno Assay) devices, then the question usuallybeing of a mass survey, or research devices, the question being of asingle research of a small series only. RIA devices must be fast andtherefore they handle several samples simultaneously. A research deviceneed not be so fast but samples may, instead, be in containers orcassettes of different sizes. The radioactive isotope of the samples mayalso emit high energy radiation and therefore the detector of a researchdevice must be larger and the lead shield must be much better than in aRIA device.

Either well-type or diametrically through hole-type detectors aregenerally used in counters. Well-type detectors are provided with ahollow, formed in the detector material, in which the sample isinserted. In hole-type detectors a hole goes through the detectormaterial into which the sample is lifted. A well-type detector is easierto manufacture. It also has better efficiency and it is easier to shieldthan a hole-type detector.

Known gamma counters have been presented e.g. in the US patentpublications U.S. Pat. Nos. 4,029,961 and 4,035,642. In these devicesthe sample vials to be measured have been placed in cassettes of tenvials and the measuring device takes one cassette at a time formeasuring. As there are ten gamma detectors in the device, all samplesin the cassette can be measured simultaneously. However, this kind ofdevice is only suitable for use in RIA measurements because it wouldbecome too large and expensive for use in research if manufactured usingknown technique. Moreover, one cannot use a well-type detector in thiskind of device because the sample is lifted into the detector.

For economical reasons, research devices have only one large and wellshielded detector. Since it has not been possible to combine RIA devicesand research devices, those isotope laboratories which want to do bothRIA counting and actual gamma research have been forced to purchase twoseparate counters. Therefore, for economical reasons, counters are alsomanufactured with 1, 2, or 4 detectors. They are larger and bettershielded than necessary in actual RIA work and therefore they can, to acertain extent, be also used in research work. However, the drawback inRIA work is lower speed compared to actual RIA devices and limitedefficiency in research work. Furthermore, the volume of samples cannotexceed that of RIA samples.

SUMMARY OF THE INVENTION

The object of this invention is to provide a new sample changermechanism in such a gamma counter wherein sample containers and theircassettes are of different sizes. The sample changer mechanism accordingto the invention is characterized in that the changer mechanismcomprises a grip unit and a lifting device for lifting and transferringthe sample from the transfer unit to the measuring unit, and that thegrip unit is provided with grip elements for transferring samples ofdifferent sizes based on the information obtained from the identifyingunit.

The other characteristics of the invention have been set forth in theensuing claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in the following by means of exampleswith reference to the accompanying drawings in which

FIG. 1 shows an axonometric view of a gamma counter according to theinvention.

FIG. 2 shows the gamma counter of FIG. 1 viewed from the side.

FIG. 3 corresponds to FIG. 2 and shows the gamma counter moving a samplecontainer into the measuring unit.

FIG. 4 shows a sectional view taken along the line A--A in FIG. 2.

FIG. 5 shows sample container cassettes, being movable on the transfertable, of the gamma counter of FIG. 4.

FIG. 6 shows the sample cassette, viewed from the end, at a positionwhere the samples are being lifted into the measuring unit.

FIG. 7 shows the end of the sample cassette of FIG. 6 viewed from theside.

FIG. 8 corresponds to FIG. 6 and shows another embodiment of the samplecassette.

FIG. 9 shows the end part of the sample cassette of FIG. 8 viewed fromthe side.

FIG. 10 corresponds to FIG. 6 and shows a third embodiment of the samplecassette.

FIG. 11 shows the end of the sample cassette of FIG. 10 viewed from theside.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an axonometric view of a gamma counter according to theinvention, the principal functional parts being a measuring unit 50 anda lifting device 40 consisting of a transfer device unit 30 and a gripunit 20, belonging thereto, for the sample container holders. Thetransfer device unit 30 is mounted on a cantilever beam 41 integral withvertical part 49 which can be moved in vertical direction in order tolift a sample container holder out of the sample container cassette andto lower it into the measuring unit 50.

The grip unit 20 consists of a slide 31 moving on a horizontal guide bar42, the slide having three pairs of grip nails 24 attached thereto.These form the three grip elements 21, 22, and 23, being of differentsizes, for gripping the holders, being of different widths, of samplecontainers.

The measuring chamber of the measuring unit 50 is provided with only asingle big hole 53 for the detector. The gamma counter in FIG. 1 is,therefore, meant for use in research and it can take sample containersof different sizes in cassettes of different sizes one at a time foranalysis. Generally in research use there is no need to measure manysamples simultaneously. Instead, the radioactive isotope of the samplesmay emit high energy radiation and therefore the detector of a researchdevice must be large and the lead shield must be massive andthick-walled.

Operation of the device of FIG. 1 is described in greater detail in thefollowing figures.

FIG. 2 shows the main parts of the gamma counter of FIG. 1 viewed fromthe side. Samples 10, including sample container cassettes 11, whichcontain sample container holders 15 and, inside them, sample containers17, are placed in the cassette transfer unit 60 on the measuring table61, being in connection with a conveyor which moves one cassette at atime to a position for lifting the sample containers. In FIG. 3 itslocation is in the left corner of the measuring table 61, the cassette11 being shown as a cross-sectional view. In this gamma counter one canuse sample containers and their cassettes of three different sizesbecause the grip unit 20 has three grip elements 21, 22, and 23 ofdifferent sizes.

The lifting device 40 accomplishes the transfer of samples to themeasuring unit 50 for measuring. The transfer unit 30 is moved on ahorizontal guide bar 42 of the cantilever beam 41 by means of a coggedbelt 47 and an electric motor 46. Based on information obtained from acassette identifier, locating on the cassette path before the measuringpoint, the slide 31 in the transfer unit 30 moves so that a grip elementof the right size is right above the cassette. It can be seen in thefigure that the smallest of the grip elements 21, 22, and 23 has beenselected i.e. the one with the reference number 21. The grip nails 24will subsequently lift the sample container holder 15 out of thecassette 11. The vertical movement has been arranged so that the wholecantilever beam 41 rises on the guide bars 48.

FIG. 3 illustrates a situation where the transfer unit 30 of the gammacounter has moved the holder 15 of the sample container in horizontaldirection right above the measuring hole 53 of the measuring unit 50.After this the cantilever beam 41 on the whole is lowered, the samplecontainer going down into the measuring hollow 53 having a well-typedetector 55. The measuring unit 50 has such a construction that themeasuring chamber 51, being made of lead, is provided with a hollow ofthe same size as the detector 55. The detector has been installed bylowering it downward from above into its hollow and mounting aprotective ring 57 on top. The advantage of the construction is that,whenever necessary, one can easily change the detector from above.

FIG. 4 shows the gamma counter of FIG. 1 viewed from above. In thefigure the table 61, having the measuring unit 50 in the middle, formsthe cassette transfer unit 60. The measuring unit has a measuringchamber 51 containing one detector. Sample container cassettes 11, 12,and 13 of different widths are placed on the table 61 where they aretransferred in turn for measuring by means of conveyors 62. Thecassettes rotate along a path round the measuring unit 50. A transducer65 for identifying cassettes has been placed on the path, before themeasuring point, the transducer identifying the width of the cassetteand the size of the sample containers therein and controlling that asuitably sized grip element is transferred close to the sample. Thisdevice is suitable for research work where simultaneous measurement ofmany samples is generally not required, but the detector is large enoughand the walls of the measuring chamber are thick enough.

FIG. 5 shows three sample container cassettes 11, 12, and 13 ofdifferent sizes. Their lengths are the same but the widths aredifferent. The width of the cassette defines the size of samplecontainers it can take. The narrowest cassette 11 can take ten smallsample containers along with their holders. The cassette is thenprovided with the corresponding number of recesses for the samplecontainers. A medium wide cassette takes eight medium-sized samplecontainers and the widest cassette takes five wide sample containers.The gamma counter shown in FIG. 1 can measure all sample container sizesmentioned above. To identify cassettes of different sizes the end partsof all cassettes have been provided with identification parts 1 and 2.The transducer, placed in connection with the transfer unit, identifiesthe width of the cassette by the form of the identification part.

The sample container cassette 11 is schematically shown in FIG. 6 on thetable 61 of the transfer unit 60 at a position where the samples arelifted up. It is seen in the figure that there is a guide 64, raisingfrom the surface of the table, formed along the path on the table. Acorresponding recess has been formed on the cassette 11 so that, on thelower edge of the cassette, a guide edge 18 is formed, the widthcorresponding the distance between the guide 64 on the table and theedge 63 of the table. When the guide edge 18 of the cassette moves inthe groove between the guide and the table edge, the cassette stayssideways firmly in place with its other side leaning against the edge 63of the measuring table. The forward transfer movement of the cassette isperformed so that the nail of the pulling device inside the table edge63 grips the opening 14 on the side wall of the cassette. At the sametime, this nail of the pulling device, in the opening of the cassette,prevents the cassette from rising, the cassette being held firmly on thepath 61 also in vertical direction.

FIG. 7 shows as a side view that end of the cassette which comes firstto the place where the samples are to be lifted. As shown in the figure,the cassette is provided with two identification parts 1 and 2 by meansof which the transducer 65 shown in FIG. 4 identifies the width of thecassette. In this cassette both parts are closed and so the transduceridentifies the cassette to be a thin type. Figure also shows the hole 14for the nail of the pulling device locating on the side of the cassette.

FIG. 8 shows a medium wide cassette 12. It is shown in the figure thatthe guide 64 on table 61 and the nail of the pulling device lock alsothis cassette firmly in place on the path. This is due to the fact thatthe guiding edge 18 in the lower edge of the cassette is quite similarto that of a thin cassette, apart from the fact, that the recess underthe cassette is wider which is due to the greater width of the cassette.So, one can reliably move cassettes of different widths on the transferpath as long as the width of the guiding edge 18 in their lower edgecorresponds to the distance of the guide 64 of the table and the edge 63of the table from each other.

It can be seen also in FIG. 9 that a medium wide cassette 12 has beenmarked for the identification transducer in such a way that only theupper identification part 1 is closed.

FIG. 10 shows a wide cassette 13 whose control is performed exactly inthe same way as that of the other cassettes. Only the identificationparts are different, as seen in FIG. 11. In this case only the loweridentification part 2 is closed.

It can be seen in FIGS. 6, 8, and 10 that the other side of thecassettes 11, 12, and 13 leans against the same edge 63 of the measuringtable 61 so that the middle part of a wider sample cassette remainsfarther away from the edge than that of a narrow cassette. This distanceof the middle part from the edge 63 is marked with letters a, b, and cin the figures.

Since the distance of the middle part of the cassette i.e. a,b, and cvaries, the cassette transfer unit in a gamma counter of FIGS. 1 and 2has been designed to operate so that the slide on the horizontal guidebar is controlled by the information obtained from the identificationtransducer. Firstly, the right grip element is chosen out of the gripunits 21, 22, and 23 shown in FIG. 2. After that, the middle part of thechosen grip element is moved to a distance a, b, or c from the edge 63.Now, the cassette can be moved so that the holder of the samplecontainer moves between the nails 24 of the grip element 21 and thelifting of the sample can start thereafter.

It is obvious to a specialist that the different embodiments of theinvention can vary within the scope of the ensuing claims.

We claim:
 1. Changer mechanism for individual measurement of radioactivesamples in a gamma counter, the changer mechanism comprising:anidentifying element for identifying different sizes of samplecontainers; a device for transferring the sample containers each heldwithin a respective sample container holder to a measuring unit formeasuring and back therefrom after measuring, the device fortransferring comprising a lifting device having a grip unit for liftingand transferring the sample container holder from a transfer unit to themeasuring unit, the grip unit comprising a plurality of grip elementsfor gripping and transferring sample container holders of differentsizes, each of said plurality of grip element corresponding to adifferent size sample container holder; and means for selecting one ofsaid plurality of grip elements to grip and transfer a correspondingsample container holder based on size information obtained from theidentifying element.
 2. The changer mechanism according to claim 1,wherein each of said plurality of grip elements of the grip unit isprovided with grip nails for gripping at least one edge of a respectivesample container holder holding a sample container and wherein there areas many grip elements as there are sizes of sample containers.
 3. Thechanger mechanism according to claim 1 or 2 wherein the grip unit of thelifting device is disposed on a horizontal guide bar and is moved on theguide bar according to size information from the identifying element sothat a suitably sized grip element is selected to move to a respectivesample container holder holding a sample container so as to grip thesample container holder.
 4. The changer mechanism according to claim 1or 2 wherein relative to a horizontal plane, a respective samplecontainer holder holding a sample container is situated principally atthe same level when initially gripped by the grip unit and when measuredin the measuring unit.
 5. The changer mechanism according to claim 3wherein relative to a horizontal plane, a respective sample containerholder holding a sample container is situated principally at the samelevel when initially gripped by the grip unit and when measured in themeasuring unit.
 6. The changer mechanism according to claim 1 or 2,further comprising sample container cassettes of different widthsholding a plurality of sample container holders on said transfer unit.7. The changer mechanism according to claim 6, further comprising meansfor rotating said sample container cassettes along a path of travel onsaid transfer unit around the measuring unit.
 8. The changer mechanismaccording to claim 7, wherein said identifying element is a transducerpositioned along said path of travel of said sample container cassettes.9. The changer mechanism according to claim 7, wherein each samplecontainer cassette comprises at least one identification part at an endof the cassette such that said identifying element can identify the sizeof said sample container holders contained therein based on said atleast one identification part.